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Ancient Time Capsule: Scientists Discover DNA in 6-Million-Year-Old Turtle Shell

The researchers found preserved bone cells in the carapace, which exhibited structures like the nucleus of a cell, where DNA traces were found. Credit: Dr. Edwin Cadena, Universidad del Rosario and STRI

There are seven existing speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>species of sea turtles, with the genus Lepidochelys comprising two of them: the olive ridley and the Kemp’s ridley. Despite being among the most common sea turtles in much of the Caribbean Sea and elsewhere, these species have a largely mysterious history and evolutionary background. Recently, the discovery of a turtle shell fossil on the Caribbean coast of Panama has shed light on their ancient past, representing the oldest fossil evidence of these turtles to date.

A Glimpse into the Miocene Epoch

The discovery of the fossil in the Chagres Formation indicates that this turtle lived approximately 6 million years ago in Panama in the upper Miocene Epoch, a time when the world was getting cooler and drier, with ice accumulating at the poles, sea levels falling, and reduced rainfall.

The remains were analyzed by a team of paleontologists led by Dr. Edwin Cadena of the Universidad del Rosario in Bogotá, Colombia, who is also a research associate at the Smithsonian Tropical Research Institute in Panama.

Field Work in Piña Beach

Fossil remains of a turtle shell from 6 million years ago were found in Piña Beach, on the Caribbean coast of Panama. Credit: Carlos De Gracia, University of Vienna and STRI

In addition to finding the oldest record of Lepidochelys turtles, the researchers discovered something unexpected in the fossil bones of this turtle: traces of DNADNA, or deoxyribonucleic acid, is a molecule composed of two long strands of nucleotides that coil around each other to form a double helix. It is the hereditary material in humans and almost all other organisms that carries genetic instructions for development, functioning, growth, and reproduction. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>DNA. After detecting preserved bone cells (osteocytes) with nucleus-like structures, they used a solution called DAPI to test for the presence of the genetic material.

“Within the entire vertebrate fossil record on the planet, this had only been previously reported in two dinosaur fossils, including one of Tyrannosaurus rex,” Dr. Cadena pointed out, referring to the ancient DNA.

Implications for Molecular Paleontology

This discovery gives the fossil vertebratesVertebrates are animals that have a backbone and include mammals, birds, reptiles, amphibians, and fish. They have a more advanced nervous system than invertebrates, allowing them greater control over their movements and behaviors, and they are able to move and support their body weight using their spine. Vertebrates are found in many habitats and play important roles in the ecosystem as predators, prey, and scavengers.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>vertebrates preserved on the Caribbean coast of Panama enormous importance not only for understanding biodiversity at the time of the emergence of the Isthmus of Panama, which divided the Caribbean from the Pacific and joined North and South America, but also for understanding the preservation of soft tissues and possible original living matter such as proteins and DNA, essential components of an emerging field known as Molecular Paleontology.

“The Caribbean fossils from Panama that we have managed to rescue over the years are helping to rewrite the history of marine vertebrates of the Isthmus,” said Carlos De Gracia, co-author of the study and a doctoral fellow affiliated with STRI who is funded by Panama’s Office for Science and Technology (SENACYT).

Reference: “An Upper Miocene marine turtle from Panama that preserves osteocytes with potential DNA” by Edwin-Alberto Cadena, Carlos De Gracia and Diego A. Combita-Romero, 23 November 2023, Journal of Vertebrate Paleontology.
DOI: 10.1080/02724634.2023.2254356

This research resulted from cooperation between the Smithsonian Tropical Research Institute and the Faculty of Natural Sciences of the Universidad del Rosario. 

The study was funded by the Universidad del Rosario and the National Secretary of Science and Technology of Panama. 

Source: SciTechDaily